Snow spiders

Earlier this week, on a mild afternoon, I was working on my computer while Dan had taken Raven out for some exercise. I was startled by a sharp rap on my window. When I peered out, Dan was gesturing for me to come down: he’d found something he thought I might be interested in.

It turned out to be a spider, curled up on the surface of the snow. It was less than a centimetre long with all its legs tucked in to its body, and how he spotted it I don’t know. It was out in the middle of the milkweed fields, so I can only presume that it came out of one of the milkweed pods, or maybe up through a hole in the snow at the base of one of the stems. It would have been a long way for it to walk from other potential origins.

I started out trying to ID it by going to BugGuide.net and doing a search for “snow spider”. And lo and behold, there it was! Along with quite a number of other spiders on snow. I’m fairly certain this is a Ground Spider, family Gnaphosidae, maybe in the genus Gnaphosa, and could possibly be G. parvula. I make this identification based on the dimples/pale spots in the slightly-flattened top of the abdomen (others I looked at had rounder abdomens and/or lacked dimples). Another possibility that occurs in our area is G. muscorum, except that’s supposed to have a pale patch at the front/top of the abdomen. Really, though, I’m waiting for its identification by an expert at BugGuide.

In the meantime, while looking up whether Gnaphosa sp. are even active in the winter, I found this pdf article called the Phenology of Winter-active Spiders. The opening sentence states that there are 54 species of winter-active spiders in southern central Canada (the author was from Manitoba) and the article discusses the life cycle of each. The only Gnaphosa he mentions is G. muscorum, and all of his specimens for the species were collected in May-June-July (though all the species in his report are ones that are supposed to be active in the winter). So I may have to wait for an ID on BugGuide.

I ran off a few photos of Dan’s spider, then started walking back to the house. As I returned, I kept an eye on the ground, to see if any other critters might pop up (recalling also the caterpillar from a few weeks ago). No caterpillars, but I did find a second spider. Assuming it was the same as the first, I just ran off a few shots with the idea of posting one on the blog, following the first and saying “hey look, I found another.” When I got the photos uploaded onto my computer and looked at the spiders at about 20 times life size, I became pretty certain that they weren’t the same species. Their cephalothoraxes (the heads) weren’t the same shape, for one thing. The second one’s legs were thinner than the first’s. Hmm…

Looking more closely at my selection of “snow spider” results, I spotted this species in there as well. This is a Thin-legged Wolf Spider, belonging to the genus Pardosa. There are two genera that look very similar, and can be told apart by the presence or absence of a dark V on the cephalothorax. It’s absent on this one, therefore it’s Pardosa. The pdf mentioned above also had two Pardosa species listed. Neither of them were encountered in the winter, either.

This spider wasn’t found out on the snow, it came in on a piece of firewood. Dan also found this one and called me downstairs to see if I was interested. It’d probably been quite happily tucked away in the stacks of firewood in the garden “shed”. Very long-legged and delicate-looking, this is a Long-bodied Cellar Spider, Pholcus phalangioides, and is one of the most common household spiders. Originally native to the tropics, it’s now found in much of the world. It’s often one of the most abundant in any given house (or cellar, or woodshed). They build webs, and when disturbed will shake their web violently in an attempt to startle or confuse predators.

Their long-legged nature really only confuses them with one other type of arachnid, the harvestman, frequently called “daddy-long-legs”, although it turns out that both of these arachnids are sometimes known by that latter name. The specific name of the cellar spider, phalangioides, originates from the roots Phalangium (the genus containing harvestmen) and “-oides” which is Greek for “similar to” or “resembling”.

Cellar spiders are great for pest control. In particular, they will prey on other spiders, often species that are much bigger than they are. I found one comment on BugGuide suggesting that this would be a useful thing for folks living in Arizona and other places where venomous spiders may be a consideration. Encourage the cellar spiders to set up shop and it’ll help keep your other spider populations down! When food is scarce, they’ll turn cannibalistic, feeding on others of their species.

Here’s a neat series of shots submitted to BugGuide, of a cellar spider and its prey, which the photographer unwrapped and cleaned to see what it was.

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20 responses to “Snow spiders”

That is so cool! I’m surprised yet delighted to learn they’re out and about that far north, especially with snow still on the ground. Seeing them in winter isn’t strange down here, but I’d have thought the situation up there would be different. But 54 species? Wow.

And that first image… What a handsome spider! Great photos all, but that one really captivates me.

Never thought about snow spiders before! Guess anything’s possible, isn’t it? I was interested in learning about the cellar spiders and that they are “good” spiders! I’ll have to keep my eye out for them! ~ks

I ran into a trashline orbweaver like this one http://bugguide.net/node/view/236785 on Friday, and it displayed the startle response characteristic of the species: shaking its web so that it became indistinguishable from its oscillating trashline. Then I had a thought: the only other web-shaking response I’ve witnessed was from a spined micrathena http://bugguide.net/node/view/308462. Then it hit me that these two species have the most peculiar body shapes I’ve ever seen. Each has an unlikely-seeming extension of the posterior dorsal opisthosoma.

Does this extension serve as a counterweight that makes it easier for the spider to shake its web? Do you know of any research that’s been done to answer this question? I posted the same question on Bug Guide, but I thought you might have some ideas.

hmmm thats interesting! i found a spider in my bathtub, it looks a lot like the long bellied cellar spider but the spider i found had a light green butt. I havent been able to find anything online. hopefully it is one of these good spiders since i live in las vegas, nevada and we have a lot of brown recluse and black widows living here.

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Seabrooke Leckie
I am a biologist and naturalist, writer and photographer, but most of all a lover of nature. I live on 130 rural acres in eastern Ontario, surrounded by woods and meadows that are my inspiration. I try to hike our land nearly every day, and I always carry my camera with me. I enjoy sharing my discoveries here.
More about me.